A novel waste paper cellulose-based Cu-MOF hybrid material threaded by PSS for lithium extraction with high adsorption capacity and selectivity

As the most abundant green and renewable resource in nature, cellulose has received the researchers' attention because of its excellent properties. In this work, waste paper cellulose with high length-to-diameter ratio and rich hydroxyl groups was utilized as template for the preparation of Cu-MOF/PSS hybrid material (Cu-MOF: Cu-3(BTC)(2), BTC = 1,3,5-benzenetricarboxylate; PSS: Polymer polystyrene sulfonate), where the Cu-MOF was well-threaded by PSS polymers. Afterwards, the obtained cellulose-based Cu-MOF/PSS hybrid material (WP@PSS@Cu-MOF) was used for Li+ ion extraction in brine solution and some adsorption experiments were carried out to evaluate its adsorption behavior. The results indicated that it had an obvious selectivity and high adsorption capacity for Li+ ion. It also confirmed that the introduction of PSS into Cu-MOF matrix greatly improved the selectivity and adsorption capacity for Li+ ions due to the synergy between the size-sieving effects from Cu-MOF and special binding affinity from PSS polymer. However, it was found that an excessive PSS addition easily led to the residual Cu(OH)(2) phase and negatively affected the formation of Cu-MOF crystals, causing the reduction of capturing sites for Li+ ions. As a whole, this work provided a green and simple strategy to utilize low-cost biomass as template material to fabricate some absorbents that have great potential for applications in the adsorption and separation fields.